The Mexican president is under pressure to explain why a company associated with the country’s first high-speed rail contract owns a mansion apparently designed for the presidential family and described by his actor wife as the “real family home” in a society magazine interview.

The revelations, published on Sunday on the website of leading Mexican journalist Carmen Aristegui, have opened a new front against Enrique Peña Nieto, who is already struggling to deal with the fallout from the disappearance and probable massacre of 43 students six weeks ago. Many observers claim the government’s long-standing tolerance of corruption is part of the background to the current security crisis.

The modernist white mansion boasts seven bedrooms, marble floors, a spa, a lift, an underground garage and mood lighting that can bathe the building in pink, violet and orange. Located in an exclusive neighbourhood of Mexico City, it has been valued it at about $7m (£4.4m).

The crux of the investigation rests on the discovery that the mansion is registered under the name of Ingenieria Inmobiliaria del Centro, a company owned by Grupo Higa, which is also associated with the Chinese-led consortium that was awarded a $3.7bn contract on 3 November to build a high-speed rail link between the capital and the city of Queretaro.

Mexico’s president is embroiled in a scandal over a mansion with links to a Chinese-led consortium awarded the contract to build the first high-speed train in Mexico. Photograph: Hector Guerrero /AFP/Getty Images

The government stunned investors last Thursday when it rescinded the contract, citing the need to address existing accusations of favouritism. These included complaints about the participation of Grupo Higa, which is headed by a personal friend of the president and, according to the Aristegui report, benefited from contracts worth $652m while Peña Nieto was governor of Mexico State between 2005 and 2011.

The president’s office responded quickly to the revelations with a statement claiming that the president’s wife, Angelica Rivera, was in the process of buying the property from the company for an unspecified price. The house, it notes, is built on two adjacent lots that back on to a house already owned by Rivera, a popular telenovela actor who met Peña Nieto when she was contracted to promote his administration in the State of Mexico as he was preparing his presidential bid. The couple married in November 2010.

The statement said Rivera made a down payment of 30% in January 2012, almost a year before her husband became president and that “the objective” was “to increase the space of her own home.” The statement stresses that Rivera “is economically solvent and has sufficient resources to buy the properties”.

The statement cites a 2013 article in Hola magazine as proof that there has never been any attempt to hide the house. Hola photographed Rivera in the mansion she refers to as the “real home” to which the family will return when they leave the presidential residence at the end of Peña Nieto’s term in 2018.

The mansion at the centre of the political spat borders property already owned by Angelica Rivera, the wife of the Mexican president. Photograph: Hector Guerrero/AFP/Getty Images

These answers have not satisfied critics. “The response of the presidency is full of gaps, holes and lacunae that need to be clarified,” political analyst Denise Dresser told said on Arisegui’s breakfast radio show on Monday. “The central point is that the house belongs to a company that has again and again received benefits from the Peña Nieto government.”

Critics said the statement ignored the report’s allegations that the house was specifically designed for the couple and their six children – three each from previous marriages.

This was confirmed by the building’s architect, Miguel Angel Aragones. In a television interview in October 2013, he said it had been “a real delight” working directly with Peña Nieto, who he described as “a first rate guy; intelligent, sensitive, respectful, and friendly”.

Aristegui’s website said it was refused an interview with the architect because a confidentiality agreement meant he was unable to discuss the house.